An actuator is a device utilized to move or control a mechanism of system. Electromagnetic actuators are operated by a source of energy, namely and electric current, and convert that energy into motion. FIGS. 1 and 2 illustrate known three-prong and single prong actuators 10, 20, respectively. As shown therein, the actuators 10, 20 generally include a stator 22 and an armature 24 configured for rotational or pivoting movement relative to the stator 22. The armature 24 and stator 22 are typically manufactured from high permeability material, such as steel. The armature 24 typically includes one or more prongs 26. For example, the armature 24 in FIG. 1 has three prongs 26 while the armature in FIG. 2 has a single prong 26. The stator 22 may include two or more legs, around one of which a coil of wire 28 is fitted. In operation, current is introduced into the coil 28 to produce an electromagnetic force which is used to attract the hinged armature 24 to the stator 22 to rotate the armature 24.
As will be readily appreciated, when the coil 28 is energized, a magnetic field is created 360 degrees around the coil. The magnetic flux of the magnetic field circles through the metal armature 24 (and through the tips of the prongs 26) and stator 22, causing a magnetic attraction between the armature 24 and stator 22 to rotate the armature 24. With the three-prong actuator 10 of FIG. 1, substantially all of the magnetic flux generated by energizing the coil 28 is captured by the by the armature 24 and stator 22, and directed therethrough to generate a closing force to rotate the armature 24 towards the stator 22. Single prong actuators, however, like the actuator 20 shown in FIG. 2, are unable to capture all of the generated magnetic flux. In particular, as shown therein, magnetic field lines 30 emanating from one side of the coil 28, which wrap around to the other side of the coil 28 are lost, i.e., they are not collected by the armature 24 nor stator 22 and, therefore, do not contributed to the production of the rotating force or torque.
As will be readily appreciated, three-prong actuator designs have armatures 24 and stators 22 that combine to cover about 75% of the circumference of the coil 28. In contrast, single and two-prong actuator designs have armatures 24 and stators 22 that combine to cover only about 35% of the circumference of the coil 28, with the single prong designs having a less efficient magnetic path, as illustrated in FIG. 2. As a result, three-prong actuators typically have a much stronger closing force than their two-prong or single-prong counterparts.
In certain applications, where size is of concern, single prong actuator designs must sometimes be utilized. The work output (i.e., generated torque or closing force) of such single-prong actuators suffers, however, due to the large amount of low-permeability air surrounding almost 75% of the coil circumference.
Accordingly, there is a need for an actuator having an enhanced magnetic structure that provides increased work output or closing force compared to known actuators of similar size and type.